Electrochemical systems have practical uses as sensors, fuel cells and electrolytic cells. Electrochemical cells used as fuel cells provide an environmentally clean method for generating electricity. Each cell is formed from a plurality of components connected to each other in electrically conductive communication. Fuel cell systems can be formed by stacking and electrically connecting at least two electrochemical cells together to provide power generation for residential, commercial and industrial scale power applications. As a result of assembling multiple electrochemical cells in stacks, the dimensional tolerances associated with the fabrication of cell components can accumulate thereby creating a potential for undesirable shifting of the components. The dimensions of sealing components within the electrochemical cell also vary as the temperature of the cell changes and as forces acting on the electrochemical cell change. This can lead to leakage of fuel from the electrochemical cell and reduced electrical output. In addition, when separate components are used to compensate for dimensional tolerance, the overall number of component parts in an electrochemical cell increases, thereby increasing the complexity of assembly.
Sealants including gaskets and adhesives such as dielectric adhesives have been used to join components of electrochemical cells. Sealants have a tendency to erode or degrade over time, thereby becoming less effective. Sealants are, generally placed on or applied to sealing areas of cell components leaving other portions of the components disposed within the periphery of the sealing area free of sealants. Selective use of sealants in this manner can cause a gap to form between the portions of the cell components which have no adhesive applied thereto. For example in an active area of a cell component where the electrochemical reactions occur, generally no sealant is applied. Therefore, in the cell active areas an unintended gap, approximately equal to the thickness of the sealant, can occur between adjacent cell components. Electrochemical cell designs which utilize sealants have, therefore included additional components dedicated to compensating for the dimensional offsets or gaps, thereby increasing the overall number of components and the difficulty of assembling an electrochemical cell. Moreover, use of dielectric adhesives can result in the need to provide further components to provide for electrical conductivity within the electrochemical cell. Furthermore, dielectric adhesives are limited for use in applications with low temperature operating conditions thus limiting the applications in which they can be used.
Electrochemical systems generally include two catalytic electrodes in contact with an electrolyte medium forming a generally pliable electrode-electrolyte assembly. The electrode-electrolyte assemblies can contract or expand depending on the amount of water retained therein. For pliable electrode-electrolyte assemblies, support devices for maintaining a desired shape of the electrode-electrolyte assembly are typically used within an electrochemical cell. However, because the dimensions of the electrode-electrolyte assembly vary due to variations in the amount of water retained therein and due to forces applied thereto, dimensional compensating components have been used in addition to the support device. Selection of an appropriate material for dimensional compensating components is difficult because such components must be electrically conductive and capable of elastic deformation. A porous form of graphitic carbon has been used for manufacture of dimensional compensating components. However, graphitic carbon has a relatively low tensile strength and is known to degrade in electrochemical cell applications. The prior art has not disclosed a unitary metallic component which both effectively compensates for dimensional variations of and provides support for the electrode-electrolyte assembly.
Assembly of electrochemical cells can be difficult because of the need to join many individual components together in sealing engagement while providing means for compensating for variations in the dimensions of the components during operation. Assembly of electrochemical cells is further complicated because electrical connections which are required between certain cell components are typically formed during assembly.
There is a need to provide an electrochemical cell with a reduced number of components and which perform superior to graphitic carbon materials to improve: compensation for dimensional offsets, support for electrode-electrolyte assemblies, uniformity of distribution of process fluids, manufacturability, strength, corrosion resistance, assembly reliability, sealing capability, electrical contact during operation. Prior art methods and systems for addressing these needs were either too expensive, inefficient, or ineffective or a combination of all of these. Based on the foregoing, it is the general object of the present invention to improve upon or overcome the problems and drawbacks of the prior art.